Gas turbines utilize components known as buckets (or blades) for generating rotational energy from hot compressed gases. The turbine buckets are mounted to the perimeter of a turbine rotor wheel, which can rotate about the centerline axis of the engine. As hot combustion gases exit the combustor and flow across the turbine buckets, the turbine rotor wheel rotates. In doing so, energy from the hot combustion gases is converted to rotational energy, which may be utilized to drive electrical generators or may provide direct mechanical work, for example.
Materials used to construct the turbine rotor wheel can differ from other turbine components, and in many designs, the turbine rotor wheel is not as resistant to heat as the buckets that are directly exposed to the hot combustion gases. As a result, the high temperatures of the hot combustion gases can exceed the metallurgical limitations of the turbine rotor wheel, causing thermal stresses, oxidation, and structural cracking
To prevent the turbine rotor wheel from overheating, cooling air can be extracted from the compressor to cool the spaces surrounding and within the turbine rotor assembly, including those in thermal contact with the turbine rotor wheel. Extracting air in this conventional way may divert air from the combustor and may hamper the efficiency of the engine cycle.